Personally I wouldn’t put it back in the bottle, partly due to it being too much effort and also because it just doesn’t strike me as a good idea. If I’ve got loads of insulin (ie more than half a reservoir) left I sometimes just change my infusion set where it attaches to my body (because the reason for changing them regularly is to avoid scar tissue building up in your body so you need to change the set regardless of how much insulin is left) and continue to use the old tube and reservoir.
I’m all for not wasting valuable resources, but I do think there’s a limit between being thrifty and not having a life – you’re borderline at the moment 